Calculator Input Form
Use the grid below. It shows three columns on large screens, two on smaller screens, and one on mobile.
Plotly Graph
The chart shows how allowable exposure time changes as working distance changes, while other selected assumptions stay fixed.
Example Data Table
These example values illustrate how shielding, distance, and dose limits change the safe working window.
| Scenario | Dose Rate | Ref. Distance | Work Distance | Shielding | Occupancy | Dose Limit | Existing Dose | Safety | Allowable Time |
|---|---|---|---|---|---|---|---|---|---|
| Inspection cell | 1.80 mSv/h | 1.0 m | 2.0 m | 0.35 | 0.90 | 0.50 mSv | 0.08 mSv | 0.85 | 2.52 h |
| Shielded cabinet | 0.90 mSv/h | 1.0 m | 1.5 m | 0.20 | 0.80 | 0.30 mSv | 0.04 mSv | 0.90 | 3.66 h |
| Open service area | 2.40 mSv/h | 1.0 m | 3.0 m | 0.50 | 0.75 | 1.00 mSv | 0.12 mSv | 0.80 | 7.04 h |
Formula Used
How to Use This Calculator
1. Enter source dose rate
Provide the measured or stated dose rate and select the correct unit.
2. Set the geometry
Enter the reference distance where the dose rate is known, then enter the actual working distance for the task.
3. Apply shielding and occupancy
Use the shielding transmission factor for barrier reduction and the occupancy factor for partial presence in the area.
4. Define the dose budget
Enter the selected dose limit, existing accumulated dose, and a safety factor to keep the estimate conservative.
5. Review the result and graph
The page shows allowable exposure time, adjusted dose rate, projected dose, a chart, and download buttons for record keeping.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates allowable working time before a chosen dose limit is reached. It adjusts source dose rate for distance, shielding, occupancy, and safety factor, then divides the remaining allowable dose by the adjusted dose rate.
2. Why does distance matter so much?
For point-like sources, radiation intensity falls quickly as distance increases. This calculator uses the square of the distance ratio, which is a common engineering approximation for planning and comparative evaluation.
3. What is the shielding transmission factor?
It is the fraction of radiation that still passes through the shielding. A value of 0.25 means 25% of the unshielded dose rate remains after the barrier.
4. What does the occupancy factor represent?
It accounts for how much of the task period a person is actually present in the exposure area. For example, 0.50 assumes half-time occupancy.
5. Why should I use a safety factor?
It creates a conservative planning margin. A safety factor of 0.80 means the calculator only uses 80% of the remaining dose budget when estimating exposure time.
6. Can I mix µSv and mSv values?
Yes. The form converts both units automatically to a common basis. That lets you enter dose rates and dose limits without performing manual unit conversion first.
7. Is this enough for compliance decisions?
No. This is a planning aid, not a compliance instrument. Always verify procedures, actual field measurements, source geometry, detector calibration, and regulatory requirements before authorizing work.
8. What happens if remaining dose is zero?
The calculator returns zero allowable time. That means the existing accumulated dose already meets or exceeds the chosen limit, so the task assumptions or controls must change.